would this be interesting?

JDMcEachin jdm at synthcom.com
Sat Jan 11 20:34:20 CET 1997


At 08:30 PM 1/9/97 -0800, Kyle Farrell wrote:

>What i've thought about doing is having two digital oscillators and 
>switch between them at audio rates.  The user could define a point where 
>the output would switch from one oscillator to the other.  The 
>oscillator would first output waveform "A".  Then at the point in the 
>cycle where the "switch point" is reached the output would switch to 
>oscillator "B" until the end of the cycle.  The next cycle would begin 
>with "A" again.  Using a triangle and square wave you could get something 
>like this:
>
>"A":
>    --                
>   -   -              
>  -     -             
> -       -            
>-         -          -
>           -        -
>            -      -
>             -    -
>              -  -
>               --
>
>"B":
>-----------
>          |
>          |
>          |
>          |
>          |
>          |
>          |
>          |
>           ---------
>
>
>output:
>    --  ---
>   -  - | |
>  -    -| |
> -      | |
>-         |
>          |
>          |
>          |
>          |
>           --------------
>
>        ^ switch point
>
>The switch point would be modulatable by LFOs, envelopes, etc.
>
>I tried this in Csound and it was, well, different. :) It might be nasty
>with all those sharp corners on the output, but an analog filter would do
>that some good.  btw- is this at all similar to how the PPG or Prophet VS 
>work?

The PPG and VS switch waveforms on end of cycle.  All the waveform
s have the same frequency, so the fundamental frequency stays the same.
Your method has the switching on non cycle boundaries.  You're going to have
lots of high frequencies caused by the switching in mid cycle.  If the the
switching is at audio frequencies, you'll hear it as well.  Below audio,
you'll hear rhythmic thumping.  If the frequency of switching goes above the
frequency of the waves, I would guess it would be perceived as the
fundamental.  I would guess the overall effect will be kind of like ring
modulation.

>Does this seem like it would be an interesting project?  comments &
>opinion are welcome :)

Should sound pretty damn interesting, though you could use any two audio
sources.  Another thing you may want to try is using two VCAs instead of a
switch, and have a crossfade time control.  This should get rid of a lot of
the high frequency stuff, and give you a little more versatility.

Good luck w/ your degree.

JDM




More information about the Synth-diy mailing list